The communication channel between a transmitter and a receiver is susceptible to noise, interference, and multipath. Multiple antennas may be used at the receiving destination to enhance the received signal. A receiver chain for signals received at each antenna may be necessary. Therefore, multiple receiver chains may be necessary to exploit the signals received at multiple receive antennas. Use of multiple receiver chains increases the power consumption. A mobile station in a communication system may greatly benefit from receive diversity; however, mobile stations generally have limited battery power supply.
In another aspect, transmit power level of a signal targeted for a mobile station may be at a lower level when the mobile station is using receive diversity. Processing a received channel may be accomplished using receive diversity by combining the received signals. When the signals are combined at the receiver, the effective carrier to noise ratio of the channel may be increased to a level above the minimum level required for processing the channel. As a result, the transmitter may transmit the signal at a lower power level without effecting the receive processing. As such, the transmitter may be able to transmit to a larger number of mobile stations. Use of receiver diversity at the mobile station thus increases the capacity of the communication system; however, use of receiver diversity increases the power consumption at the mobile station.
Performance of mobile stations, in at least one aspect, is measured with respect to the length of time operating without recharging the battery power supply. To benefit from the receive diversity, the receiver may have to turn on multiple receiver chains to process multiple received signals. As a result, the receiver may consume a substantial amount of battery power. Therefore, use of receive diversity without any rules for decoding a received channel may adversely effect the battery life of the mobile station.
To this end as well as others, there is a need for an effective use of receiver diversity for decoding various channels in a communication system.